ICAO recommends that aircraft stands are illuminated to an average horizontal illuminance of at least 20 lux. However, simply stating “20 lux” does not tell the whole story.
Illuminance must be measured on a defined plane. On an aircraft stand, the two main measurements are horizontal illuminance and vertical illuminance.
Both are measured in lux, but they assess different parts of the working environment and are measured in different ways.
Horizontal illuminance measures the light falling onto a horizontal surface.
On an aircraft stand, this normally means the apron surface. It helps determine how clearly people can see:
To measure horizontal illuminance, a lux meter is positioned horizontally with the sensor facing upwards.
The commonly referenced ICAO recommendation for aircraft stands is:
This means that achieving a 20 lux average is not enough on its own. The lighting must also be reasonably even across the stand.
For more information, read our guide to what apron floodlighting uniformity means.
Vertical illuminance measures the light falling onto an upright surface.
On an aircraft stand, it helps determine how clearly people can see:
Vertical illuminance is commonly assessed at a height of 2 metres above the apron surface.
The lux meter is held vertically, but the direction it faces matters. A reading taken facing a floodlight may be much higher than one taken facing away from it.
The lighting design or survey should therefore state which directions are being assessed, such as towards the aircraft, terminal or main working area.
The simplest explanation is:
Horizontal illuminance helps people see what is on the ground. Vertical illuminance helps people see what is in front of them.
| Horizontal illuminance | Vertical illuminance |
|---|---|
| Measured on a horizontal plane | Measured on a vertical plane |
| Normally assessed at apron level | Commonly assessed 2 metres above the apron |
| Shows how well the ground is lit | Shows how well people, vehicles and aircraft surfaces are lit |
| Sensor faces upwards | Sensor faces a defined direction |
Yes.
A lighting system may deliver enough light onto the apron surface while leaving people, vehicles or the side of the aircraft in shadow.
This can happen when:
This is why horizontal and vertical illuminance should be calculated separately.
An average lux value can hide dark areas.
For example, one part of the stand may be very bright while another is poorly lit. The overall average may still appear acceptable.
A complete aircraft stand lighting assessment should therefore consider:
Simply increasing the wattage or lumen output will not always improve the result. Mast position, optical distribution and aiming are often just as important.
You can learn more in our guide to airport apron floodlighting standards.
Before carrying out an aircraft stand lighting survey, the airport should define:
Readings should be taken across the full operational area, not only beneath the floodlight masts or in the brightest locations.
The meter orientation, measurement height and location should also be recorded so that the results can be compared accurately with the lighting design.
ICAO guidance commonly referenced for aircraft stands recommends an average horizontal illuminance of 20 lux, with an average-to-minimum uniformity ratio of no more than 4:1.
Vertical illuminance on an aircraft stand is commonly assessed at 2 metres above the apron surface.
No. The 20 lux figure refers to the average horizontal illuminance. The uniformity requirement controls how low the darkest point can be.
Vertical illuminance is directional. The result changes depending on which way the sensor faces, so the measurement direction must be defined and recorded.
Yes. A stand may be well lit at ground level while people, vehicles and aircraft surfaces remain poorly illuminated.
Saying that an aircraft stand requires 20 lux does not provide enough information on its own.
Airport operators also need to know:
Horizontal and vertical illuminance measure different aspects of the lighting environment. Both should be assessed to ensure the aircraft stand is illuminated clearly and consistently for ground operations.